Investigation of the retained austenite orientation in iron precipitates of martensitic transformation

The retained austenite orientation in iron precipitates of martensitic transformation was studied in a Cu-Fe-P alloy. The alloy was isochronally aged at 723 K with tensile stresses of 0 and 16 MPa after solution treatment at 1143 K for 2 h respectively. The results showed that [220](gamma-)(Fe) and [200](gamma-)(Fe) of austenite (gamma-Fe) in iron precipitates was parallel to [220](Cu) and [200](Cu) of copper matrix during ageing without applied stress, respectively. When the ageing treatment was carried out with an applied stress of 16 MPa, the martensitic transformation occurred in the iron precipitates. For the first time, it was found that not crystal orientation of [220] but [200] of retained gamma-Fe in the iron precipitate was parallel to [220] of copper matrix, which was attributed to partial dislocations slipping and shearing coherent precipitates. The results suggest that the crystal orientation of the retained austenite in iron precipitates changes during martensitic transformation. (C) 2020 Elsevier B.V. All rights reserved.